1. Field of Invention
The present invention relates to a slim size disc clamping device particularly for DVD-ROM or CD-ROM mounted in notebook computer being fixedly maintained on a turntable when disc is rotating in high speed.
2. Related Art
Conventionally, the mechanism of employing elastic O-ring or torsion spring to bias steel balls is adopted to clamp disc. This conventional disc clamping device is shown in a top view in FIG. 1A and a sectional view in FIG. 1B respectively. As shown, elastic O-ring 14 is inserted around an outer side of a cylindrical axis 12 projected to the upper surface of turntable 10. A plurality of steel balls 18 (e.g., 3) are equally distributed along the circumference of junction of guide member 16 and turntable 10. In mounting a disc (not shown) onto turntable 10, disc is pressed down to force steel balls 18 to bias O-ring 14 toward the inside by the guidance of guide member 16 until in place. At this time, the inner periphery of disc is fixedly maintained between guide member 16 and turntable 10 by the expansion of O-ring 14 which biases steel balls 18 to original positions. The drawbacks of such design are that O-ring 51 loses its elasticity as time passes, and O-ring 14 and steel balls 18 may not engage well due to poor manufacturing quality. As a result, a fix clamp of disc is not achievable.
Another prior art disc clamping device is shown in sectional views of FIGS. 2A and 2B. As shown in FIG. 2A, disc 20 is placed on top of insertion portion 22 of turntable 10a for clamping onto turntable 10a. In mounting, press down disc 20 to force it to contact with turntable 10a so as to clamp disc 20 between disc-clamping piece 24 and turntable 10a by the guidance of disc-clamping piece 24. Then turntable 10a immediately bounces up when disc 20 is not pressed for fixedly maintaining disc 20 between and by disc-clamping piece 24 and turntable 10a (see FIG. 2A). This design is without the problem of lacking elasticity of spring as time passes. But this is still unsatisfactory for the purpose for which the present invention is concerned because the radially positioning of disc is poor. It is known that not all central holes of discs have the same tolerance. However, above design does not provide a mechanism to compensate such tolerance for providing a precise positioning. As a result, such disc clamping device is not applicable to high precision positioning products such as DVDs.
It is thus an object of the present invention to provide a disc clamping device with self lock elements particularly for DVD-ROM or CD-ROM being fixedly maintained on a turntable when disc is rotating in high speed.
The advantages of the present invention are realized by providing a disc clamping device comprising a turntable having a boss on the center for putting disc thereon; and a disc clamping member tightly sleeved on boss of turntable having a diameter nearly the same as that of the center hole of disc, and disc clamping member having a plurality of protuberances on periphery wherein protuberances are deformed inwards when biased by disc such that disc can insert through disc clamping member, and then protuberances return to original forms by elastically energized force for clamping disc on turntable.
In one aspect of the invention, the number of protuberances is three. Protuberances are spaced apart by 120 degrees each other. Protuberances may be formed integrally with disc clamping member, or alternatively formed of copper separately. An annular pad is provided on the outer periphery of the top surface of turntable for providing a frictional force to disc when rotating. Disc clamping member includes a plurality of spaced cantilever members along its periphery wherein a protuberance is located on the outer surface of a corresponding cantilever member. Preferably, the line from protuberance to the center of disc clamping member is at an angle about 10 to 60 degrees with respect to the line from base of cantilever member to the center of disc clamping member. Also, the line from the point of protuberance contacting disc to the top of protuberance is at an angle about 10 to 80 degrees with respect to a downward vertical line originated from the top of protuberance.
In another aspect of the invention, turntable is a copper and disc clamping member is a plastic. In mounting disc on disc clamping member, press down disc to force circular protuberances to bias cantilever members to cause it to deform inwards. Then disc inserts through disc clamping member to pass protuberances until contacting with pad. At this time, protuberances immediately expand outward to return to original forms by elastically energized force of cantilever members. As such, disc is clamped by protuberances and pad. Thus, disc is secured on turntable.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.